Patent GB-708007-A (GB)
Title: Improvements in or relating to the preparation of acrylic esters
IPC: C07C69/54
Filed: 1951-06-12
Abstract: An acrylic ester is obtained by reacting together at between 0 DEG and 75 DEG  C. nickel carbonyl, acetylene, an alcohol and an acid, then adding to this reaction mixture and therein reacting together at between 0 DEG  and 75 DEG  C. acetylene, carbon monoxide and a further quantity of the alcohol, the carbon monoxide supplying between 20 per cent and substantially 86 per cent of the total CO available from both carbon monoxide and nickel carbonyl.  The reaction between the nickel carbonyl, acetylene and alcohol (the stoichiometric reaction) usually results in the formation of a brownish colouration and the acetylene, carbon monoxide and alcohol are then added after this colouration has developed.  If the mixture of alcohol, nickel carbonyl and acid contains excess alcohol, the reaction may be brought about by adding carbon monoxide to the acetylene run into the mixture after the stoichiometric reaction is established, alternatively the alcohol may be added along with the acetylene and carbon monoxide after the stoichiometric reaction has started.  The process may be carried out continuously by continuously adding to the reaction mixture nickel carbonyl and acid along with the alcohol, acetylene and carbon monoxide.  The process may also be effected by adding the alcohol, carbon monoxide and acetylene to a liquid medium containing an excess of the alcohol, an acrylic ester, nickel carbonyl and acid into which acetylene is passed.  An excess of acid over nickel carbonyl may be used but it is preferred to use an excess of 1 per cent to 20 per cent nickel carbonyl over the acid and the free nickel carbonyl can be taken up in the reaction mixture in a final step by addition of acid to consume the unreacted nickel carbonyl by reaction with the alcohol and acetylene.  It is also preferred to use a stoichiometric excess of 1 to 10 per cent of acetylene over the total CO and a stoichiometric excess of alcohol of 10 to 300 per cent based on either the total CO available or the acetylene is generally advantageous.  There may also be used an inert organic solvent such as dioxane, benzene, toluene, xylene, ethylene dichloride, chloroform, carbon tetrachloride, ethyl acetate, acetone, methyl ethyl ketone or isopropyl ether and the use of such solvents is recommended when the reacting alcohol is viscous or solid.  It is preferred to use saturated monohydric alcohols ROH wherein R is an alkyl group which may be primary, secondary or tertiary, branched or straight chained, thus R may be methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, nonyl, decyl, dodecyl, hexadecyl or octadecyl or higher, in their various isomeric forms.  Other alcohols may also be used, e.g. alicyclic alcohols such as cyclohexyl, methylcyclohexyl, dicyclopentenyl, dicyclopentyl; unsaturated alcohols such as allyl, methallyl, chloroallyl, crotyl, propargyl, undecenyl, linoleyl and cinnamyl alcohols. The alcohol may also be aryl-aliphatic or alicyclicaliphatic, e.g. benzyl, methyl benzyl, butylbenzyl, phenylethyl, b -cyclohexylethyl, hexahydrobenzyl or tetrahydrobenzyl alcohols. The alcohol may also contain substituents such as oxygen, sulphur, nitrogen and the halogens.  Typical alcohols of this type are furfuryl alcohol, tetrahydrofurfuryl alcohol, 2,5-dimethyl - 2 - hydroxymethyl - 2,3 - dihydropyran, 2,5 - dimethyl - 2 - hydroxymethyltetrahydropyran, methoxyethanol, ethoxyethanol, ethoxypropanol, ethoxybutanol, butoxyethanol, octoxyethanol, alloxyethanol, vinoxyethanol, methoxyethoxyethanol, butoxyethoxyethanol, phenoxyethanol, butylphenoxyethoxyethanol, cyclohexoxyethanol, benzoxyethoxyethanol, 2 - phenoxy - 1 - propanol, ethylthioethanol, butylthioethanol, phenylthioethanol; nitroalcohols such as nitroethanol, 2-nitropropanol, 2-nitrobutanol, and 2-nitro-2-phenylethanol; ketoalcohols such as acetoin, b -acetylethyl alcohol, b -hydroxyethylacetone; and cyanohydrins and halohydrins such as ethylene cyanohydrin and ethylene chlorohydrin.  Polyhydric alcohols can also be used and one or more of the hydroxyl groups reacted, typical polyhydric alcohols are ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, glycerine, ethers of glycerine, pentaerythritol, mannitol and sorbitol.  The alcohol may contain small amounts of water although with large amounts of water some free acrylic acid may result.  The acid used is preferably hydrogen chloride but hydrogen bromide is also effective.  Hydrogen fluoride containing a trace of chloride ion gives less rapid reaction whilst hydrogen iodide, phosphoric acid, and sulphuric acid give slow reactions although a small amount of chloride ion added to sulphuric or phosphoric acid accelerates the reaction.  Organic acids may also be used especially when allylically unsaturated alcohols are used as reactants thus when allyl alcohol is used best results are obtained with acetic, propionic, or acrylic acid.  Benzoic, monochloracetic, succinic, maleic and oxalic can also be used. The carbon monoxide and acetylene used should have a low content of oxygen or preferably be free of oxygen and the gases should contain no appreciable amount of sulphide or lower valency phosphorus compounds or arsine but inert gases such as carbon dioxide, nitrogen, or hydrogen merely act as diluents.  It is usually expedient to displace air from the apparatus at the start by flushing with an inert gas such as nitrogen.  A polymerization inhibitor such as b -naphthol, pyrogallol or resorcinol may be added to the reaction mixture.  In examples (1) acetylene, anhydrous hydrogen chloride and nickel carbonyl are passed into a mixture of methyl acrylate and methanol and after a brown colour has developed the rate of introduction of acetylene is increased and carbon monoxide and methanol are pumped into the reaction mixture which is held at 45 DEG C. by cooling, methyl acrylate containing a small amount of methyl propionate is isolated from the mixture and polymerizes readily upon heating with benzoyl peroxide; (2) acetylene, excess ethanol, nickel carbonyl and anhydrous hydrogen chloride are passed into a mixture of ethyl acrylate and ethanol and after a brown colouration has developed the flow of acetylene is increased and carbon monoxide introduced, the temperature being maintained at 40 DEG  C.; ethyl acrylate containing a small amount of ethyl propionate is isolated from the reaction mixture and polymerizes quickly on heating with benzoyl peroxide; in an alternative procedure the reaction mixture in the main reaction vessel is allowed to overflow to a smaller vessel to which alcohol is fed in an amount of 5 per cent of the theoretical requirement for the reaction, sufficient hydrogen chloride to react with nickel carbonyl left unreacted in the main reaction vessel, and acetylene, and the reaction mixture from this smaller vessel is then treated for the isolation of ethyl acrylate, the process being kept in continuous operation for two weeks; (3) a reactor system is arranged so that all the reactants are fed continuously into the reaction mixture stream prior to its passage through a pump which circulates the mixture through a water-jacketed tube, into a surge vessel, and back to the pump. The reactor is charged with isopropyl acrylate and isopropanol, flushed air-free with nitrogen, and acetylene, hydrogen chloride, nickel carbonyl and isopropanol introduced through the pump. After a brown colour has developed the acetylene rate is increased and carbon monoxide admitted, the acetylene and carbon monoxide flow rates being increased at intervals to final rates which are maintained while additional isopropanol is introduced, the level in the reactor being kept constant by continuous withdrawal from the surge vessel and the mixture treated after removal of unreacted nickel carbonyl for recovery of isopropyl acrylate; (4), (5), (6), (7), (9), (10) n propyl acrylate, m butyl acrylate, sec.-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate and n-decyl acrylate respectively are obtained by a process similar to that used in (3) the corresponding acrylate and alcohol being employed.  Detailed examples-(8), (11), (12), (13)-are also given for the production of tertiary butyl acrylate (as initial acrylate being used in this case) n-dodecyl acrylate, 2 (1,3,3-trimethyl butyl) 5,7,7-trimethyloctyl acrylate, and stearyl acrylate (chiefly n-octadecyl acrylate) respectively.  In (11), (12) and (13) the initial mixture comprises the appropriate alcohol and ethyl acrylate whilst in (13) acetone is also present in the initial mixture.